Concrete Made from Waste. A concrete product made from waste fly ash from coal-fired electric plants is now available in the United States. Autoclaved cellular concrete (ACC) is made from fly ash, lime, cement, aluminum powder, and water. When these ingredients are combined, a chemical reaction occurs that causes the formation of hydrogen bubbles, prompting the material to double in size. The product is then cut into pieces and cured in an autoclave, which gives it strength, rigidity, and durability characteristics. Used for half a century in Great Britain and Germany, ACC's documented benefits include being 25% lighter and an R-value of 1.25 per in. (twice that of conventional concrete). Its cost is reported to be about the same as conventional concrete, and its first U.S. applications are expected to be residential foundations. ACC is 75% fly ash, and about 70 million tons of this waste material are produced by electric utilities each year. Popular Science, July 1993, 2 Park Avenue, New York, NY 10016. Tel: (212)779-5000; Fax: (212)779-9468.

Nails and R-Value. A research project conducted by Dow Chemical has revealed that metal fasteners such as nails can reduce the R-value of foam sheathing by as much as 20%. Researchers constructed two 8-ft., steel-frame wall sections, each filled with R-13 fiberglass batts, with gypsum board interiors and stucco exteriors. One wall was sheathed with 1/2 in. fiberboard; the other with 1 in. of extruded polystyrene. Metal fasteners were used to attach the metal lath for the stucco exteriors on both walls; these 11/2 in. fasteners were installed on 8-in. centers, penetrating through the foam or waferboard. Each wall was then tested in a guarded box, according to ASTM testing procedures. The wall with extruded polystyrene had an R-value of only R-3.9, higher than the other wall, rather than the R-4.8 that one might expect, due to metal bridging of the fasteners. Researchers admit that this 20% loss would be a small portion of the house's overall heat loss (about $10 a year for gas heating systems). However, in buildings relying exclusively on foam sheathing for insulation, the energy penalty associated with thermal bridging would be about seven times higher. Energy Design Update, August 1993, Cutter Information Corp., 37 Broadway, Arlington, MA 02174. Tel: (617)648-8700; Fax: (617)648-8707.

European Appliances. U.S. manufacturers are designing appliances that are more energy- and water-efficient than their predecessors, but they still haven't reached the efficiency levels of European designs. For example, many Europeans use a cooktop with solid cast-iron heating elements, which, because they retain heat for a long time, use less energy. And where U.S. homes use ovens that are often too big for what we cook in them, European units are smaller and they also rely on convection, which reduces baking time by about 30%, doesn't require preheating, and allows for lower baking temperatures. Dishwashers are also smaller, yet can accommodate a 12-place setting of dishes. One model uses 7.5 gallons of water; another, large enough for six place settings, uses only 3.6 gallons. In contrast, the most energy-efficient U.S. dishwashers use 7.5 to 9 gallons. Front-loading washing machines, small enough to be placed under a bathroom sink, consume only half the water of U.S. models. Some spin as fast as 1,500 revolutions per minute, compared to domestic units at 400 to 700 rpm, which allows clothes to dry more quickly by extracting more water. European appliances can cost twice as much as their U.S. counterparts, but their energy and water savings are reported to make them cost-effective investments. Buzzworm, September 1993, 2305 Canyon Blvd., Suite 206, Boulder, CO 80302. Tel: (303)442-1969.

Vacuums and Allergens. Vacuum cleaners have varying abilities to retain airborne allergens, but those that don't perform well can be modified to be more effective, according to a study conducted by researchers at the University of Virginia Health Sciences Center. The researchers tested nine vacuums--three canisters, three uprights, two water-filter units, and one high-efficiency particle arrestor (HEPA) unit--for their ability to retain a cat dander allergen. Each unit collected dust containing 40-50 mg of cat dander allergen and was placed in a sealed laboratory room and run for 15 minutes. Researchers collected air samples while the vacuums were running and for 15 minutes after. The water-filter models leaked less than 2.5 micrometers of allergens, an amount that was reduced with an electrostatic filter. Canisters leaked more allergens, from 6 to 20 micrometers, and uprights 2-15 micrometers. One canister with a double-thick bag showed minimal allergen emission. Another canister leaked considerably around the connection between the hose and bag. By adding a double-thick bag and an electrostatic filter to this unit, researchers reduced allergen leakage to less than 2 nanograms per cubic meter. They concluded that allergic consumers should test a vacuum to determine its ability to capture allergens as well as how airborne allergen levels are affected by its use. Indoor Air Quality Update, August 1993, Cutter Information Corporation, 37 Broadway, Arlington, MA 02174. Tel: (617)648-8700; Fax: (617)648-8707.

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